The long term objective of this Fogarty International Research Collaboration Award proposal is to establish a collaboration in support of the PI's parent grant, "Microfabricated Conductimetric Glucose Sensor". The aim of the parent grant is to develop a miniature sensor for the in vivo monitoring of glucose, for the treatment of insulin-dependent diabetes mellitus. The key element of the sensor is a glucose-responsive hydrogel, formed by immobilizing the enzyme glucose oxidase within a pH- responsive hydrogel. The activity of the immobilized enzyme, and its stability directly affect measures of sensor performance such as detection limit, sensitivity, range, response time and shelf life. The co- investigator, a bioanalytical chemist, brings to the project expertise in the area of enzyme immobilization and characterization, which he has applied to the development of bioanalytical systems, such as one for measuring analytes glucose in serum samples. The specific aims of this project are (i) to prepare 10 to 100 micromoles diameter beads of the glucose-responsive hydrogels used in the glucose sensor, to facilitate characterization of the enzymatic activity; (ii) to incorporate the beads into a reactor and characterize the activity of the immobilized glucose oxidase; and (iii) to construct a miniature reactor and detector system using silicon micromachining technology. The first two specific aims will extend the parent grant by providing a better characterization of the materials used in construction of the glucose sensor than was originally proposed. The final specific aim will extend the parent grant, by initiating the development of small, low cost bioanalystical systems which could be used for public health applications such as clinical analysis, or food and water quality.